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First Lady Michelle Obama handled the 'Top Ten' list on the 'Late Show with David Letterman' Tuesday night. It dealt with gardening at the White House.

First lady Michelle Obama was on the “Late Show with David Letterman” Tuesday night in honor of the publication of her new book, “American Grown: The Story of the White House Kitchen Garden.” She delivered the Top 10 list: Top 10 Fun Facts About Gardening. How did it go? Was she funny?

Well, you can watch it here, and make your own conclusion. From our point of view, she was funny, since the Letterman writers could wring a laugh out of anything. (Our favorite was No. 4: “If you have an actual green thumb, it might be scurvy.”) But she wasn’t FUNNY, if you know what we mean. The chuckle-meter wasn’t set to “stun.”

Mainly that’s because gardening is not inherently humorous. Names for Newt’s moon colony, Joe Biden nicknames – those are topics with comedy juice. Gardening is all heirloom mulch and where-should-we-put-the-salvia. It’s earnest and good for you. That’s hard to mock. Or hard to mock without going too far. Mrs. Obama might as well have been doing “Top 10 Fun Facts about Fresh Air.”

(OK, we did like the bit about “Weed Whacker One.” But “gardening was invented in 1822 by Albert Gardener”? That’s too subtle for our taste.)

Also, the first lady can’t just let fly with the yuks. She’s got a positive, restrained image to uphold. There’s a reason she’s got the highest approval rating in the White House – 65 percent in the latest CNN poll. Her husband is probably wondering if he can dump Joe and run her as VP.

That’s probably why the list touched only tangentially on fighting obesity. (No. 7: “In his lifetime, the average American will eat half a radish.”) New York Mayor Michael Bloomberg’s proposal to ban big sodas has become kind of a partisan flash point. Conservatives see it as an example of big government going too far. Liberals see it as an example of right-size government going too far. A poll shows a majority of New Yorkers oppose the move. So the whole issue of the government telling you what to consume is fraught, at the moment.

In the past, Mrs. Obama’s “Let’s Move” initiative to get kids to exercise has drawn some grumbling about nannyism from the right. So she has had to be careful what she says about sodageddon. She has said she rejects a “one-size-fits-all” approach to fighting fat, and thus would not support a federal soda ban. But at an event on Tuesday she added that “we applaud anyone who’s stepping up to think about what changes work in their communities.”

So that’s why the Letterman list wasn’t “Top 10 New Manhattan Soda Sizes.” Got any ideas for that one? (Or for Joe Biden nicknames?) Leave them in comments below.